Main Bearing and Rod Bearing Selection
NOTE: The engine bearings are of the precision insert type. The bearings are available for service use in standard and various undersizes.
CAUTION: Do not scrape, shim, or file bearing inserts. If the bearing surface of the insert is touched with bare fingers, the skin oil and acids will etch the bearing surface.
1. Inspect the bearing surfaces for the following conditions:
^ Wear.
^ Gouges.
^ Embedded foreign material. If you find foreign material, determine its nature and source. Inspect the oil pan sludge and residue.
^ Uneven side-to-side wear. If you find uneven wear, check for a bent crankshaft or tapered bearing journals.
2. Inspect the outer surfaces for the following conditions:
^ Wear. Surface wear indicates either movement of the insert or high spots in the surrounding material (spot wear).
^ Overheating or discoloration
^ Looseness or rotation indicated by flattened tangs and wear grooves
3. Inspect the thrust surfaces of the main thrust bearing for the following conditions:
^ Wear
^ Grooving (Grooves are caused by irregularities of the crankshaft thrust surface.)
CAUTION: If bearing failure is due to other than normal wear, investigate bearing failure carefully. Inspect the crankshaft or connecting rod and the bearing bores carefully.
4. Inspect the connecting rods or main bearing bores using the following procedure:
a. Tighten the bearing cap to specifications.
b. Measure the bore for taper and out of round.
c. No taper or out of round should exist.
5. Measure the bearing clearance accurately in order to determine the correct replacement insert size. There are two methods to measure bearing clearance. Method A gives more reliable results and is preferred.
NOTE: Method A yields measurement from which the bearing clearance can be computed. Method B yields the bearing clearance directly. Method B does not give any indication of bearing run-out. Do not mix inserts of different nominal size in the same bearing bore.
6. Choose a method of bearing clearance measurement.
In order to measure bearing clearance using Method A, use the following procedure:
1. Measure the journal diameter with a micrometer in several places, approximately go degrees apart. Average the measurements.
2. Measure the taper and runout. Refer to Engine Mechanical Specifications for allowable limits.
3. Install the bearing inserts. Tighten the bearing cap bolts or nuts to specification. Refer to Engine Mechanical Specifications.
IMPORTANT:
^ The bearing cap must be tightened to specification when the measurement is taken. Refer to Engine Mechanical Specifications.
^ Measure the connecting rod ID in the same direction as the length of the rod.
4. Measure the ID with an inside micrometer.
5. Select a set of bearing inserts that will produce the desired clearance.
6. If the specified clearances cannot be met, the crankshaft journal must be reconditioned. Install undersized bearing inserts. Replace both bearing shells as a set.
In order to measure bearing clearance using Method B, use the following procedure:
1. Clean the used bearing inserts.
2. Install the used bearing inserts.
3. Place a piece of gaging plastic across the entire bearing width.
Notice: In order to prevent the possibility of cylinder block or crankshaft bearing cap damage, the crankshaft bearing caps are tapped into the cylinder block cavity using a brass, lead, or a leather mallet before the attaching bolts are installed. Do not use attaching bolts to pull the crankshaft bearing caps into the seats. Failure to observe this information may damage a cylinder block or a bearing cap.
4. Seat the bearing cap carefully by lightly tapping the bearing cap with a suitable tool.
5. Install the bearing cap bolts or nuts.
TIGHTEN
^ Tighten the main bearing cap bolts evenly to 50 Nm (37 lb. ft.).
^ Turn the main bearing cap bolts evenly an additional 77°. Use the J 36660
^ Tighten the rod cap nuts evenly to 20 Nm (15 lb. ft.).
^ Turn the rod cap nuts evenly an additional 75°. Use the J 36660.
IMPORTANT: Do not rotate the crankshaft.
6. Remove the bearing cap, leaving the gaging plastic in place. It does not matter whether the gaging plastic adheres to the journal or to the bearing cap.
7. Measure the gaging plastic at its widest point with the scale printed on the gaging plastic package.
8. Remove all traces of the gaging plastic after measuring.
9. Select a set of bearing inserts that will produce the desired clearance. Refer to Engine Mechanical Specifications. Replace both bearing shells as a set.